The present invention relates to a method of analyzing particles in a fluid sample and more particularly to a method of analyzing biological fluid samples, such as urine, that are dilute, but without the necessity of physically creating a concentrated sample for analysis.
Heretofore the method for urine sediment examination requires the following steps: (i) urine must be poured into a tube and spun down in a centrifuge to separate the sediment from its suspending fluid; (ii) most of the cleared suspending fluid must be poured out; (iii) the sediment must be resuspended in the remaining fluid; (iv) the suspension must be transferred to and spread on a microscope slide; (v) a coverslip must be placed over the suspension on the slide; (vi) the slide must be focused under a microscope; and (vii) a number of fields of view must be searched and examined for the presence of abnormal numbers of red and white blood cells, epithelial cells, casts, bacteria, yeast, parasites, mucoid threads, crystals, etc., which compose urine sediment in various proportions depending upon the presence of disease. The steps of centrifugation (i), decantation (ii) and resuspension (iii) are used because the fluid sample is dilute. All these steps are currently performed manually. The manipulations involved frequently make the method messy and unpleasant. Spreading of the sediment suspension on the microscope slide often is uneven. When numerous sediments are viewed, prolonged peering into the eyepieces of a microscope becomes tiring. All these factors contribute to imprecision.
Other apparatus for handling biological specimens include the so-called Coulter counter. In this counter blood cells are passed in single file through an orifice and detected and counted by the manner in which they change the electric properties at the orifice. However, information from the Coulter counter is limited to the analysis of a single type of measurement. Where multiple parameter information is desired, the standard commercial way of obtaining it is by preparing a microscope slide with the cells fixed on an image plane and having a human operator or pattern recognition machine count statistically significant numbers of the cells as the cells are observed one-at-a-time on the slide through a microscope.
Other attempts have been made in recent years to provide optical analysis of particles flowing in a flow stream. For instance, Kay, et al., Journal of Histochemistry and Cytochemistry, Volume 27, page 329 (1979) shows a Coulter type orifice for moving cells in single file with the cells magnified on a vidicon. Additionally, Kachel, et al., Journal of Histochemistry and Cytochemistry, Volume 27, page 335, shows a device for moving cells in single file through a microscopic area where they are photographed. See also for instance Flow Cytometry and Sorting, Melaned et al., John Wiley & Sons 1979, Chapter 1.
U.S. patent application Ser. No. 146064 filed on May 2, 1980 now U.S. Pat. No. 4,338,024, issued on July 6, 1982 discloses an apparatus and a method for quantitative analysis of particle information.
However, none of the references cited heretofore teach or suggest a solution to the problem of analysis of particles in a dilute fluid sample, without the necessity of initially creating a concentrated sample through centrifugation, decantation and resuspension.